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julien 940267e317 feat(portal-bff): wire ADR-0013 audit pipeline to the auth lifecycle (#120)
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## Summary

Wires the audit pipeline (ADR-0013) to the auth lifecycle. The foundation was already in place (Prisma `AuditEvent` model, Postgres roles + grants, `AuditWriter.recordEvent` with `SET LOCAL ROLE audit_writer`); this PR layers a typed event surface and emits the first four events on real code paths.

### What lands

- **Typed methods on `AuditWriter`**: `signIn`, `signInFailed`, `signOut`, `sessionExpired`. Callers pass the raw Entra `oid`; hashing happens inside the writer so the salt never leaves the audit module. ADR-0013 explicitly defers adding these typed methods "as the matching feature ships" — auth has shipped, so we add the four events tied to code paths that exist today.
- **`HashUserIdService`** — reads `LOG_USER_ID_SALT` once at injection, exposes `hash(userId)` → 16-hex-char digest used by both `audit_events.actor_id_hash` (ADR-0013) and the future Pino `user_id_hash` (ADR-0012). Same salt + same input ⇒ same output ⇒ join key between the two streams.
- **`LOG_USER_ID_SALT` env var** promoted from the "future vars" block in `.env.example` to the active section, with the same boot-time validator pattern as `SESSION_SECRET` / `SESSION_ENCRYPTION_KEY`: mandatory, base64url, ≥ 32 bytes decoded, placeholder rejected. Wired in `main.ts`.
- **`AuditModule` is now `@Global()`** and also provides `HashUserIdService`. The previous in-line comment said "imported globally by AppModule" but the decorator was missing — without it, AuthController and the absolute-timeout middleware couldn't inject `AuditWriter` without re-importing AuditModule.
- **Emission points**:
  - `/auth/callback` happy path → `auth.sign_in` after `session.save()` (blocking per ADR-0013 §"Blocking writes": a failed audit fails the sign-in).
  - `/auth/callback` failure paths → `auth.sign_in.failed` with a discriminator `failureKind` (`entra-error`, `missing-code-or-state`, `no-pre-auth-cookie`, or any of the `AuthCodeFlowError` kinds — `state-mismatch`, `flow-expired`, `token-exchange-failed`).
  - `/auth/logout` (authenticated only) → `auth.sign_out` before `session.destroy()` — once destroy runs we lose the actor id.
  - Absolute-timeout middleware → `auth.session.expired` with `reason: 'absolute'` and `ageMs` for forensic granularity.

### Out of scope (next PRs)

- The other four v1 events from ADR-0013's catalogue (`auth.session.revoked`, `auth.token.validation.failed`, `auth.mfa.assertion.failed`, `authz.deny`) — no triggering code path exists today. They land with the admin "logout everywhere" route, downstream API access (ADR-0014), and the eventual `@RequireMfa()` / `@RequireAdmin` guards.
- Idle-timeout expiry is intentionally silent — Redis lets the key disappear with no BFF observation point. Per ADR-0010.
- Separate `AUDIT_DATABASE_URL` connection pool with `audit_writer`-only credentials — ADR-0013 marks it as the production hardening step, deferred behind `SET LOCAL ROLE` in v1.
- Retention purge job + startup self-test probe — deferred to the on-prem infrastructure ADR per ADR-0013.

### Notable choices

- **No CLS-populating middleware.** ADR-0013 anticipates an interceptor that puts `actorIdHash` on the request CLS so `AuditWriter.recordEvent` can pick it up automatically. For the four call sites in this PR, every emission path already has the user object in hand, so we pass `actorIdHash` explicitly via the typed methods and skip the middleware. It can land later when more routes need it.
- **Blocking on the happy path = strict ADR posture.** `audit.signIn` is awaited before the 302; a Postgres outage makes the sign-in fail (5xx) rather than silently producing an un-audited session. That's "no audit ⇒ no action" applied to authentication itself. Matches ADR-0013 §"Blocking writes" verbatim.
- **`signInFailed` skips the actor hash by default.** Most failure paths reject before any claim is parsed (state mismatch, expired flow). The interface accepts an optional `actor` for the rare identity-after-rejection case (future MFA assertion failure, etc.).

### Test plan

- [x] `pnpm nx test portal-bff` (clean env) → **142/142 pass** (was 123; +19 new specs across `check-log-user-id-salt`, `hash-user-id.service`, `audit.service` typed-methods, `auth.controller`, `absolute-timeout.middleware`).
- [x] `pnpm nx lint portal-bff` → clean.
- [x] `pnpm nx build portal-bff` → clean.
- [x] **CI clean-env repro** (lesson from #115/#116/#117): every env var unset → tests still 142/142. The two module specs that previously sat on the boundary (`auth.module`, `session.module`) now bootstrap their own `@Global()` stub providers for `PrismaService` + `ClsService` so AuditWriter's transitive resolution works without booting Prisma for real.
- [ ] Manual smoke against running BFF + Postgres:
  - [ ] Sign in → `select * from audit.events where event_type = 'auth.sign_in'` returns one row with `actor_id_hash`, `subject = 'session:…'`, `payload.amr` populated.
  - [ ] Sign out → matching `auth.sign_out` row.
  - [ ] Force `SESSION_ABSOLUTE_TIMEOUT_SECONDS=5` + wait → `auth.session.expired` row with `payload.reason = 'absolute'` and `ageMs > 5000`.
  - [ ] Manual `UPDATE audit.events SET event_type = 'x' WHERE id = ...` as the BFF role → fails with "permission denied" (the role contract holds even when the migrator runs as a privileged login).

---------

Co-authored-by: Julien Gautier <julien.gautier@apf.asso.fr>
Reviewed-on: #120
2026-05-13 14:21:42 +02:00
julien c3de2340e7 feat(portal-bff): absolute-timeout middleware + user_sessions index per ADR-0010 (#115)
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## Summary

Hardens the BFF session per ADR-0010 §"TTL policy" and §"Revocation":

- **Absolute-timeout middleware** — every request that survives `express-session` runs through a new middleware that checks `req.session.absoluteExpiresAt`. Past the 12 h hard ceiling, the middleware destroys the Redis-side session, clears the `portal_session` cookie, drops the entry from the per-user index, and lets the request continue anonymously. Route-level guards (`/me`, future `@RequireAuth`) turn that into a 401 where the user actually needs auth — public routes keep serving.
- **`user_sessions:{userId}` secondary index** — a new `UserSessionIndexService` maintains a Redis set of active session ids per user. Hooked into `/auth/callback` (SADD on sign-in) and `/auth/logout` + the absolute-timeout middleware (SREM on destroy). Best-effort: a failed `SADD`/`SREM` logs a warning and the auth flow continues. No in-product consumer in this PR — the admin "logout everywhere" endpoint lands with the admin module.
- **Session payload extension** — `createdAt` and `absoluteExpiresAt` are now set on the session at the same moment as `req.session.user` (in `/auth/callback`). The `session.types.ts` declaration merging exposes them as optional `SessionData` fields.

## Notable choices

**Non-intrusive enforcement on expiry.** ADR-0010 says "returns 401"; we interpret that as "the user eventually sees a 401 when they touch something that needs auth", not "every route returns 401 the moment we notice the ceiling". The middleware destroys the session and calls `next()` — `/me` returns 401 on its own (no user on the session), public routes stay accessible. Validated with the project lead 2026-05-12.

**Express middleware exposed via DI, not a NestJS `MiddlewareConsumer`.** Same pattern as `SESSION_MIDDLEWARE`: factory inside `SessionModule`, resolved from the application context in `main.ts` with `app.get<RequestHandler>(SESSION_ABSOLUTE_TIMEOUT_MIDDLEWARE)`. Keeps the wiring co-located with the session middleware and avoids the `AppModule.configure(consumer)` boilerplate for a one-off enforcement layer.

**Best-effort index maintenance.** `UserSessionIndexService.add` / `remove` catch Redis errors and log a Pino warning instead of throwing. Rationale (per ADR-0010): the index is a convenience for admin operations, not a security invariant — a Redis hiccup must not break sign-in / sign-out. Orphans (entries pointing to keys that have expired idle-TTL on their own) are tolerated and will be filtered by future consumer code.

**Per-user index identifier = Entra `oid`.** Stable per-user inside the tenant, matches `req.session.user.oid`. Admin "logout user X" will work against this same key. Future multi-tenant scenarios may want `${tid}:${oid}` — easy refactor when External ID activation lands (ADR-0008).

## Out of scope (next PRs)

- Admin "logout everywhere" endpoint consuming `UserSessionIndexService.list(userId)`. Waits on the admin module + `@RequireAdmin` / `@RequireMfa` guards.
- Audit-pipeline first-class events for `session.absolute_timeout` and `user_session_index.*` (ADR-0013). For now they're structured Pino logs.
- Token blob persistence (id_token / access_token / refresh_token) in the encrypted session — ADR-0014 dependency.

## Test plan

- [x] `pnpm nx test portal-bff` → **123/123 pass** (was 110 before; +13 specs across new `user-session-index.service.spec.ts`, `absolute-timeout.middleware.spec.ts`, and added cases in `auth.controller.spec.ts`).
- [x] `pnpm nx lint portal-bff` → clean.
- [x] `pnpm nx build portal-bff` → clean webpack build.
- [x] Prettier-clean for all touched files.
- [ ] Manual smoke against running BFF:
  - [ ] Sign in normally → Redis has `session:<id>` + `user_sessions:<oid>` SISMEMBER returns `<id>`.
  - [ ] Logout → both keys gone.
  - [ ] Forge a past `absoluteExpiresAt` in Redis (or shorten `SESSION_ABSOLUTE_TIMEOUT_SECONDS=5` in `.env`) → next request after expiry returns 401 on `/me`, cookie cleared, index entry SREM-ed.

---------

Co-authored-by: Julien Gautier <julien.gautier@apf.asso.fr>
Reviewed-on: #115
2026-05-12 23:23:14 +02:00